iterate over list while changing it

Thu Sep 24 18:20:16 EDT 2009

On 2009年9月24日 21:32:53 +0100, Torsten Mohr <tmohr at s.netic.de> wrote:
> Hello,
>> a = [1, 2, 3, 4, 5, 6]
>> for i, x in enumerate(a):
> if x == 3:
> a.pop(i)
> continue
>> if x == 4:
> a.push(88)
>> print "i", i, "x", x
>> I'd like to iterate over a list and change that list while iterating.
> I'd still like to work on all items in that list, which is not happening
> in the example above.
> The conditions in the example are not real but much more complex
> in reality.
>> Can anybody tell me how to do this?

Generally, don't. It's much less dangerous to create a new list as you
go.
new_a = []
for x in a:
 if x != 3:
 new_a.append(x)
 if x == 4:
 new_a.append(88)
 # or whatever you intended "push" to mean
If you weren't doing the insertion, you could have used a list
comprehension and neatened things up a bit.
-- 
Rhodri James *-* Wildebeest Herder to the Masses